Seamless voice call initiation

ABSTRACT

Methods, devices, and system related to wireless communications are disclosed. In one example aspect, a method for wireless communication includes receiving, by a first access node in a first type of communication network, a request from a wireless device to establish a voice session with an Internet Protocol Multimedia System (IMS); initiating, by the first access node, an IMS voice session establishment for the wireless device; configuring, by the first access node, a Quality of Service (QoS) for the IMS voice session using a Protocol Data Unit (PDU) session modification request; and determining, in part based on one or more capabilities of the wireless device, to refrain from triggering a fallback to a second type of communication network for the IMS voice session establishment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Pat. Application No.17/384,583, titled “SEAMLESS VOICE CALL INITIATION,” filed Jul. 23,2021, which is hereby incorporated by reference in its entirety.

BACKGROUND

Voice over New Radio (VoNR) is a voice calling service that uses the 5Gnetwork for its source of Internet Protocol (IP) voice processing.Similar to Voice over Long-Term Evolution (VoLTE), VoNR is based on theIP Multimedia System (IMS) according to the Third-Generation PartnershipProject (3GPP) standard.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed descriptions of implementations of the present invention willbe described and explained through the use of the accompanying drawings.

FIG. 1 is a block diagram that illustrates a wireless communicationssystem.

FIG. 2 illustrates an example Evolved Packet System (EPS) fallbackprocedure for IMS voice defined in current 3GPP standard.

FIG. 3 illustrates an example procedure for initiating IMS voiceestablishment in accordance with one or more embodiments of the presenttechnology.

FIG. 4 is a flow chart representation of a method for wirelesscommunication in accordance with one or more embodiments of the presenttechnology.

FIG. 5 is a flow chart representation of another method for wirelesscommunication in accordance with one or more embodiments of the presenttechnology.

FIG. 6 is a block diagram that illustrates an example of a computersystem in which at least some operations described herein can beimplemented.

The technologies described herein will become more apparent to thoseskilled in the art from studying the Detailed Description in conjunctionwith the drawings. Embodiments or implementations describing aspects ofthe invention are illustrated by way of example, and the same referencescan indicate similar elements. While the drawings depict variousimplementations for the purpose of illustration, those skilled in theart will recognize that alternative implementations can be employedwithout departing from the principles of the present technologies.Accordingly, while specific implementations are shown in the drawings,the technology is amenable to various modifications.

DETAILED DESCRIPTION

While using 5G/NR technology for both voice and data communications isthe ultimate goal of 5G adoption, most network operators have assumed aphased approach for 5G deployments. Various 5G deployment options andtimelines for readiness of network components and devices have led to aninterim option of using Evolved Universal Terrestrial Radio Access(E-UTRAN) for voice service. The Long-Term-Evolution (LTE) EvolvedPacket System (EPS) is one of the deployment scenarios that supportredirection and/or handover to E-UTRAN during the call setup phase,referred to as the EPS fallback.

Due to the different network characteristics between the 5G/NR networksand the LTE networks, preferences can be given to the LTE networks forhandling IMS voice calling. For example, LTE networks often have largercoverage areas, enabling stable voice calls when the users are on themove. However, the call signal strength and quality provided by the5G/NR networks often surpass those of the LTE networks. This documentdiscloses techniques that enable the network to refrain from triggeringthe EPS fallback, e.g., based on UE capabilities, thereby reducing setupdelays during voice session establishment and providing better callquality and strength to users using the 5G/NR communication technology.The disclosed techniques also allow proper handover to the E-UTRAN whenthe call signal deteriorates after the voice call session isestablished.

Wireless Communications System

FIG. 1 is a block diagram that illustrates a wireless telecommunicationsystem 100 (“system 100”) in which aspects of the disclosed technologyare incorporated. The system 100 includes base stations 102-1 through102-4 (also referred to individually as “base station 102” orcollectively as “base stations 102”). A base station is a type ofnetwork access node (NAN) that can also be referred to as a cell site, abase transceiver station, or a radio base station. The system 100 caninclude any combination of NANs including an access point, radiotransceiver, gNodeB (gNB), NodeB, eNodeB (eNB), Home NodeB or eNodeB, orthe like. In addition to being a WWAN base station, a NAN can be a WLANaccess point, such as an Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 access point.

The NANs of a network formed by the system 100 also include wirelessdevices 104-1 through 104-8 (referred to individually as “wirelessdevice 104” or collectively as “wireless devices 104”) and a corenetwork 106. The wireless devices 104-1 through 104-8 can correspond toor include network entities capable of communication using variousconnectivity standards. For example, a 5G communication channel can usemillimeter wave (mmW) access frequencies of 28 GHz or more. In someimplementations, the wireless device 104 can operatively couple to abase station 102 over a Long-Term Evolution (LTE) /LTE Advanced (LTE-A)communication channel, which is referred to as a 4G communicationchannel. In some implementations, the base station 102 can providenetwork access to a Fifth-Generation (5G) communication channel.

The core network 106 provides, manages, and controls security services,user authentication, access authorization, tracking, Internet Protocol(IP) connectivity, and other access, routing, or mobility functions. Thebase stations 102 interface with the core network 106 through a firstset of backhaul links 108 (e.g., S1 interfaces) and can perform radioconfiguration and scheduling for communication with the wireless devices104 or can operate under the control of a base station controller (notshown). In some examples, the base stations 102 can communicate, eitherdirectly or indirectly (e.g., through the core network 106), with eachother over a second set of backhaul links 110-1 through 110-3 (e.g., X1interfaces), which can be wired or wireless communication links.

The base stations 102 can wirelessly communicate with the wirelessdevices 104 via one or more base station antennas. The cell sites canprovide communication coverage for geographic coverage areas 112-1through 112-4 (also referred to individually as “coverage area 112” orcollectively as “coverage areas 112”). The geographic coverage area 112for a base station 102 can be divided into sectors making up only aportion of the coverage area (not shown). The system 100 can includebase stations of different types (e.g., macro and/or small cell basestations). In some implementations, there can be overlapping geographiccoverage areas 112 for different service environments (e.g.,Internet-of-Things (IoT), mobile broadband (MBB), vehicle-to-everything(V2X), machine-to-machine (M2M), machine-to-everything (M2X),ultra-reliable low-latency communication (URLLC), machine-typecommunication (MTC)), etc.

The system 100 can include a 5G network and/or an LTE/LTE-A or othernetwork. In an LTE/LTE-A network, the term eNB is used to describe thebase stations 102 and in 5G new radio (NR) networks, the term gNBs isused to describe the base stations 102 that can include mmWcommunications. The system 100 can thus form a heterogeneous network inwhich different types of base stations provide coverage for variousgeographical regions. For example, each base station 102 can providecommunication coverage for a macro cell, a small cell, and/or othertypes of cells. As used herein, the term “cell” can relate to a basestation, a carrier or component carrier associated with the basestation, or a coverage area (e.g., sector) of a carrier or base station,depending on context.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and can allow access by wireless deviceswith service subscriptions with a wireless network service provider. Asindicated earlier, a small cell is a lower-powered base station, ascompared with a macro cell, and can operate in the same or different(e.g., licensed, unlicensed) frequency bands as macro cells. Examples ofsmall cells include pico cells, femto cells, and micro cells. Ingeneral, a pico cell can cover a relatively smaller geographic area andcan allow unrestricted access by wireless devices with servicesubscriptions with the network provider. A femto cell covers arelatively smaller geographic area (e.g., a home) and can providerestricted access by wireless devices having an association with thefemto cell (e.g., wireless devices in a closed subscriber group (CSG),wireless devices for users in the home). A base station can support oneor multiple (e.g., two, three, four, and the like) cells (e.g.,component carriers). All fixed transceivers noted herein that canprovide access to the network are NANs, including small cells.

The communication networks that accommodate various disclosed examplescan be packet-based networks that operate according to a layeredprotocol stack. In the user plane, communications at the bearer orPacket Data Convergence Protocol (PDCP) layer can be IP-based. A RadioLink Control (RLC) layer then performs packet segmentation andreassembly to communicate over logical channels. A Medium Access Control(MAC) layer can perform priority handling and multiplexing of logicalchannels into transport channels. The MAC layer can also use Hybrid ARQ(HARQ) to provide retransmission at the MAC layer, to improve linkefficiency. In the control plane, the Radio Resource Control (RRC)protocol layer provides establishment, configuration, and maintenance ofan RRC connection between a wireless device 104 and the base stations102 or core network 106 supporting radio bearers for the user planedata. At the Physical (PHY) layer, the transport channels are mapped tophysical channels.

As illustrated, the wireless devices 104 are distributed throughout thesystem 100, where each wireless device 104 can be stationary or mobile.A wireless device can be referred to as a mobile station, a subscriberstation, a mobile unit, a subscriber unit, a wireless unit, a remoteunit, a handheld mobile device, a remote device, a mobile subscriberstation, an access terminal, a mobile terminal, a wireless terminal, aremote terminal, a handset, a mobile client, a client, or the like.Examples of a wireless device include user equipment (UE) such as amobile phone, a personal digital assistant (PDA), a wireless modem, ahandheld mobile device (e.g., wireless devices 104-1 and 104-2), atablet computer, a laptop computer (e.g., wireless device 104-3), awearable (e.g., wireless device 104-4). A wireless device can beincluded in another device such as, for example, a drone (e.g., wirelessdevice 104-5), a vehicle (e.g., wireless device 104-6), an augmentedreality / virtual reality (AR/VR) device such as a head-mounted displaydevice (e.g., wireless device 104-7), an loT device such as an appliancein a home (e.g., wireless device 104-8), a portable gaming console, or awirelessly connected sensor that provides data to a remote server over anetwork.

A wireless device can communicate with various types of base stationsand network equipment at the edge of a network including macroeNBs/gNBs, small cell eNBs/gNBs, relay base stations, and the like. Awireless device can also communicate with other wireless devices eitherwithin or outside the same coverage area of a base station viadevice-to-device (D2D) communications.

The communication links 114-1 through 114-11 (also referred toindividually as “communication link 114” or collectively as“communication links 114”) shown in system 100 include uplink (UL)transmissions from a wireless device 104 to a base station 102, and/ordownlink (DL) transmissions, from a base station 102 to a wirelessdevice 104. The downlink transmissions can also be called forward linktransmissions while the uplink transmissions can also be called reverselink transmissions. Each communication link 114 includes one or morecarriers, where each carrier can be a signal composed of multiplesub-carriers (e.g., waveform signals of different frequencies) modulatedaccording to the various radio technologies. Each modulated signal canbe sent on a different sub-carrier and carry control information (e.g.,reference signals, control channels), overhead information, user data,etc. The communication links 114 can transmit bidirectionalcommunications using FDD (e.g., using paired spectrum resources) or TDDoperation (e.g., using unpaired spectrum resources). In someimplementations, the communication links 114 include LTE and/or mmWcommunication links.

In some implementations of the system 100, the base stations 102 and/orthe wireless devices 104 include multiple antennas for employing antennadiversity schemes to improve communication quality and reliabilitybetween base stations 102 and wireless devices 104. Additionally, oralternatively, the base stations 102 and/or the wireless devices 104 canemploy multiple-input, multiple-output (MIMO) techniques that can takeadvantage of multi-path environments to transmit multiple spatial layerscarrying the same or different coded data.

Refrain From EPS Fallback

The EPS fallback refers to the deployment scenario in which the EPSsupports redirection and/or handover from the 5G Radio Access Network(NG-RAN) to E-UTRAN during the call setup phase. The EPS fallbackmechanism leverages the existing IMS Core and EPS for delivering voiceor video services. As the EPS fallback relies on the E-UTRAN and theexisting IMS core network for voice/video services, the customerexperience is the same as VoLTE except with call setup delays that areincurred as a result of the redirection/handover to the E-UTRAN. FIG. 2illustrates an example EPS fallback procedure 200 for IMS voice definedin current 3GPP standard.

Operation 1: The User Equipment (UE) camps on the NG-RAN. An IMS voicesession establishment has been initiated.

Operation 2: The network initiates Protocol Data Unit (PDU) Sessionmodification to setup Quality of Service (QoS) flow for IMS voice.

Operation 3: The NG-RAN is configured to support EPS fallback for IMSvoice and decides to trigger fallback to EPS, taking into account UEcapabilities, indication that redirection for EPS fallback for voice ispossible, network configuration, and/or radio conditions. The NG-RAN canoptionally initiate measurement report solicitation from the UEincluding E-UTRAN as target.

Operation 4: The NG-RAN responds indicating rejection of the PDU Sessionmodification to setup QoS flow for IMS voice received in Operation 2 byPDU Session Response message towards the Packet Data Network Gateway ofControl Plane and the Session Management Function (PGW-C+SMF), or HomeSMF with PGW-C via Visited SMF in case of roaming scenario, via theAccess and Mobility Management Function (AMF) with an indication thatmobility due to fallback for IMS voice is ongoing.

Operation 5. NG-RAN initiates either handover or Access Network (AN)Release via inter-system redirection to EPS, taking into account UEcapabilities.

Operation 6: When the UE is connected to EPS:

-   6a. In the case of 5GS to EPS handover and in the case of    inter-system redirection to EPS with N26 interface, the UE initiates    the Tracking Area Update (TAU) procedure; or-   6b. In the case of inter-system redirection to EPS without N26    interface, if the UE supports Request Type flag “handover” for PDN    connectivity request during the attach procedure and has received    the indication that interworking without N26 is supported, then the    UE initiates Attach with PDN connectivity request with request type    “handover”.

Operation 7: After completion of the mobility procedure to EPS, theSMF/PGW re-initiates the setup of the dedicated bearer for IMS voice.

Operation 8: The IMS voice session establishment is continued.

As indicated in Operation 3, the decision to trigger the EPS fallbackcan be based on the radio conditions using the measurement reportstransmitted from the UE. To avoid back and forth handover between thetwo networks, the 3GPP also specifies that at least for the duration ofthe voice call in EPS, the E-UTRAN is configured to not trigger anyhandover back to 5GS. However, while the LET network can provide largercoverage areas than the current 5G networks, the signal strength and/orquality of the 5G networks often surpass the LTE networks. Thus, the EPSfallback can be erroneously triggered, leading to unnecessary call setupdelays and worse call quality without the opportunity to switch back tothe 5G network.

This patent document discloses techniques that can be implemented invarious embodiments to improve the EPS fallback procedure so as toprovide better call quality to users with devices capable of both 5G andLTE communication technologies. In particular, given that the UEsupports the 5G technology, the network can be configured to refrainfrom the EPS fallback during the initiation of the IMS voice sessionestablishment to avoid the additional call setup delays. Once the callsession is established, the network can determine, based on factors suchas coverage levels, user mobility patterns, and network conditions,whether a handover of the voice call to the LTE network is necessary.

FIG. 3 illustrates an example procedure 300 for initiating an IMS voiceestablishment in accordance with one or more embodiments of the presenttechnology.

Operation 301: The User Equipment (UE) camps on NG-RAN. An IMS voicesession establishment has been initiated.

Operation 302: The network initiates Protocol Data Unit (PDU) Sessionmodification to setup Quality of Service (QoS) flow for IMS voice.

Operation 303: The NG-RAN examines UE’s capabilities and determines thatthe UE can support 5G communications. Thus, even when EPS fallback forvoice is possible, the NG-RAN decides to refrain from triggering EPSfallback for this UE. In some embodiments, the NG-RAN can consider thecoverage areas of the NG-RAN and/or E-UTRAN, as well as the networkmeasurement reports of both NG-RAN and/or E-UTRAN, to decide whether itshould refrain from triggering EPS fallback. For example, the NG-RAN canexamine the Reference Signal Received Power(RSRP) and Reference SignalReceived Quality (RSRQ) reported by the UE and determine that the 5Gnetwork conditions are sufficient to support the IMS voice session eventhough these results may not be superior to the measurement resultsassociated with the E-UTRAN. In some embodiments, the NG-RAN can comparethe RSRP with a predetermined threshold and determine whether thenetwork conditions are suitable. For example, an RSRP value of 116 dBmor better is often considered acceptable for a voice call. If the RSRPvalue gets below 116 dBm, the voice call can suffer from poor speechquality, and the user can experience various issues such as garbledvoice, audio mute, call setup failure and/or call drop. In someembodiments, using advanced codecs, such as Enhanced Voice Services(EVS), Adaptive Multi-Rate Wide Band (AMR-WB), and/or AdaptiveMulti-Rate Narrow Band (AMR-NB), the NG-RAN can decide to refrain fromtriggering EPS fallback given that the RSRP value is within an offsetrange from the predetermined threshold. For example, if the RSRP valueis within a margin of -2dBm from the threshold (e.g., 116 dBm), theNG-RAN decides to not trigger EPS fallback.

Operation 304: The IMS voice session establishment continues in NG-RAN.

Once the IMS voice session establishment is complete, the user equipmentcan perform the voice call using VoNR. When the 5G network conditionsbecome unsatisfactory (e.g., caused by UE mobility from the 5G networktowards the LTE network, or other types of changes), a systeminterworking procedure between the EPS and the 5GS can be performed. Forexample, the NG-RAN decides, at operation 305, that the UE should behanded over to the E-UTRAN. The other network functions perform relevantoperations at Operation 306 to facilitate the handover from 5GS to EPC.At Operation 306, the E-TRAN receives a handover request from theMobility Management Entity (MME) to continue the handover procedure.Such handover procedure can be the same as the N26 interface basedhandover or S1-based handover as specified in the 3GPP standard TS23.602 and/or TS 23.401.

FIG. 4 is a flowchart representation of a method 400 for wirelesscommunication in accordance with one or more embodiments of the presenttechnology. The method 400 includes, at operation 410, receiving, by afirst access node in a first type of communication network, a requestfrom a wireless device to establish a voice session with an InternetProtocol Multimedia System (IMS). The method 400 includes, at operation420, initiating, by the first access node, an IMS voice sessionestablishment for the wireless device. The method 400 includes, atoperation 430, configuring, by the first access node, a Quality ofService (QoS) for the IMS voice session using a Protocol Data Unit (PDU)session modification request. The method also includes, at operation440, determining, in part based on a capability of the wireless device,to refrain from triggering a fallback to a second type of communicationnetwork for the IMS voice session establishment. It is noted that themethod 400 is applicable to both non-roaming scenarios and roamingscenarios in which the wireless device request to establish the voicesession with the visited public land mobile network (V-PLMN). Forexample, the first access node can be located in the V-PLMN to establishthe voice session for the roaming wireless device.

In some embodiments, the method also includes determining, by the firstaccess node after the voice session establishment is complete, that ahandover procedure is required to handover the wireless device to asecond access node of the second type of communication network. In someembodiments, the first type of communication network comprises aFifth-Generation (5G) network. In some embodiments, the second type ofcommunication network comprises a Long-Term-Evolution (LTE) network. Insome embodiments, the capability of the wireless device indicates thatthe wireless device supports Fifth-Generation (5G) communicationtechnology.

In some embodiments, the determining is further based on a coveragelevel of the first type of communication network and/or the second typeof communication network. In some embodiments, the determining isfurther based on a network measurement of the first type ofcommunication network and/or the second type of communication network.

FIG. 5 is a flowchart representation of a method 500 for wirelesscommunication in accordance with one or more embodiments of the presenttechnology. The method 500 includes, at operation 510, configuring awireless device. For example, a wireless network carrier can configure awireless device so that the wireless device can operate in one or morenetworks operated by the carrier. In some embodiments, the wirelessdevice is capable of connecting to a first communication network (e.g.,the LTE network) and a second communication network that is differentthan the first communication network (e.g., the 5G network). The method500 includes at operation 520, operating a first network node in thefirst communication network. The method 500 also includes, at operation530, operating a second network node in a second communication network.The second network node is configured to receive a request forestablishing a call using an Internet Protocol (IP) Multimedia Subsystem(IMS) from the wireless device, initiate an IMS voice sessionestablishment for the wireless device, configure a Quality of Service(QoS) for the IMS voice session establishment using a Protocol Data Unit(PDU) session modification request, and determine, in part based on acapability of the wireless device, to refrain from triggering a fallbackto the first communication network for the IMS voice sessionestablishment.

It is appreciated that, the techniques disclosed herein can be used toprovide better call quality to users with devices capable of both 5G andLTE communication technologies and avoid/eliminate the unnecessarydelays in voice call establishments, thereby improving 5G technologyadoption in various scenarios under phased deployment of 5G networks.

Computer System

FIG. 6 is a block diagram that illustrates an example of a computersystem 600 in which at least some operations described herein (e.g., asshown in FIG. 4 and FIG. 5 ) can be implemented. As shown, the computersystem 600 can include: one or more processors 602, main memory 606,non-volatile memory 610, a network interface device 612, video displaydevice 618, an input/output device 620, a control device 622 (e.g.,keyboard and pointing device), a drive unit 624 that includes a storagemedium 626, and a signal generation device 630 that are communicativelyconnected to a bus 616. The bus 616 represents one or more physicalbuses and/or point-to-point connections that are connected byappropriate bridges, adapters, or controllers. Various common components(e.g., cache memory) are omitted for brevity. Instead, the computersystem 600 is intended to illustrate a hardware device on whichcomponents illustrated or described relative to the examples of thefigures and any other components described in this specification can beimplemented.

The computer system 600 can take any suitable physical form. Forexample, the computing system 600 can share a similar architecture asthat of a server computer, personal computer (PC), tablet computer,mobile telephone, game console, music player, wearable electronicdevice, network-connected (“smart”) device (e.g., a television or homeassistant device), AR/VR systems (e.g., head-mounted display), or anyelectronic device capable of executing a set of instructions thatspecify action(s) to be taken by the computing system 600. In someimplementation, the computer system 600 can be an embedded computersystem, a system-on-chip (SOC), a single-board computer system (SBC) ora distributed system such as a mesh of computer systems or include oneor more cloud components in one or more networks. Where appropriate, oneor more computer systems 700 can perform operations in real-time, nearreal-time, or in batch mode.

The network interface device 612 enables the computing system 600 tomediate data in a network 614 with an entity that is external to thecomputing system 600 through any communication protocol supported by thecomputing system 600 and the external entity. Examples of the networkinterface device 612 include a network adaptor card, a wireless networkinterface card, a router, an access point, a wireless router, a switch,a multilayer switch, a protocol converter, a gateway, a bridge, bridgerouter, a hub, a digital media receiver, and/or a repeater, as well asall wireless elements noted herein.

The memory (e.g., main memory 606, non-volatile memory 610,machine-readable medium 626) can be local, remote, or distributed.Although shown as a single medium, the machine-readable medium 626 caninclude multiple media (e.g., a centralized/distributed database and/orassociated caches and servers) that store one or more sets ofinstructions 628. The machine-readable (storage) medium 626 can includeany medium that is capable of storing, encoding, or carrying a set ofinstructions for execution by the computing system 600. Themachine-readable medium 626 can be non-transitory or comprise anon-transitory device. In this context, a non-transitory storage mediumcan include a device that is tangible, meaning that the device has aconcrete physical form, although the device can change its physicalstate. Thus, for example, non-transitory refers to a device remainingtangible despite this change in state.

Although implementations have been described in the context of fullyfunctioning computing devices, the various examples are capable of beingdistributed as a program product in a variety of forms. Examples ofmachine-readable storage media, machine-readable media, orcomputer-readable media include recordable-type media such as volatileand non-volatile memory devices 610, removable flash memory, hard diskdrives, optical disks, and transmission-type media such as digital andanalog communication links.

In general, the routines executed to implement examples herein can beimplemented as part of an operating system or a specific application,component, program, object, module, or sequence of instructions(collectively referred to as “computer programs”). The computer programstypically comprise one or more instructions (e.g., instructions 604,608, 628) set at various times in various memory and storage devices incomputing device(s). When read and executed by the processor 602, theinstruction(s) cause the computing system 600 to perform operations toexecute elements involving the various aspects of the disclosure.

Remarks

The description and associated drawings are illustrative examples andare not to be construed as limiting. This disclosure provides certaindetails for a thorough understanding and enabling description of theseexamples. One skilled in the relevant technology will understand,however, that the invention can be practiced without many of thesedetails. Likewise, one skilled in the relevant technology willunderstand that the invention can include well-known structures orfeatures that are not shown or described in detail, to avoidunnecessarily obscuring the descriptions of examples.

The terms “example”, “embodiment” and “implementation” are usedinterchangeably. For example, reference to “one example” or “an example”in the disclosure can be, but not necessarily are, references to thesame implementation; and, such references mean at least one of theimplementations. The appearances of the phrase “in one example” are notnecessarily all referring to the same example, nor are separate oralternative examples mutually exclusive of other examples. A feature,structure, or characteristic described in connection with an example canbe included in another example of the disclosure. Moreover, variousfeatures are described which can be exhibited by some examples and notby others. Similarly, various requirements are described which can berequirements for some examples but no other examples.

The terminology used herein should be interpreted in its broadestreasonable manner, even though it is being used in conjunction withcertain specific examples of the invention. The terms used in thedisclosure generally have their ordinary meanings in the relevanttechnical art, within the context of the disclosure, and in the specificcontext where each term is used. A recital of alternative language orsynonyms does not exclude the use of other synonyms. Specialsignificance should not be placed upon whether or not a term iselaborated or discussed herein. The use of highlighting has no influenceon the scope and meaning of a term. Further, it will be appreciated thatthe same thing can be said in more than one way.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” As used herein, the terms “connected,”“coupled,” or any variant thereof means any connection or coupling,either direct or indirect, between two or more elements; the coupling orconnection between the elements can be physical, logical, or acombination thereof. Additionally, the words “herein,” “above,” “below,”and words of similar import can refer to this application as a whole andnot to any particular portions of this application. Where contextpermits, words in the above Detailed Description using the singular orplural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more itemscovers all of the following interpretations of the word: any of theitems in the list, all of the items in the list, and any combination ofthe items in the list. The term “module” refers broadly to softwarecomponents, firmware components, and/or hardware components.

While specific examples of technology are described above forillustrative purposes, various equivalent modifications are possiblewithin the scope of the invention, as those skilled in the relevant artwill recognize. For example, while processes or blocks are presented ina given order, alternative implementations can perform routines havingsteps, or employ systems having blocks, in a different order, and someprocesses or blocks may be deleted, moved, added, subdivided, combined,and/or modified to provide alternative or sub-combinations. Each ofthese processes or blocks can be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks can instead be performedor implemented in parallel, or can be performed at different times.Further, any specific numbers noted herein are only examples such thatalternative implementations can employ differing values or ranges.

Details of the disclosed implementations can vary considerably inspecific implementations while still being encompassed by the disclosedteachings. As noted above, particular terminology used when describingfeatures or aspects of the invention should not be taken to imply thatthe terminology is being redefined herein to be restricted to anyspecific characteristics, features, or aspects of the invention withwhich that terminology is associated. In general, the terms used in thefollowing claims should not be construed to limit the invention to thespecific examples disclosed herein, unless the above DetailedDescription explicitly defines such terms. Accordingly, the actual scopeof the invention encompasses not only the disclosed examples, but alsoall equivalent ways of practicing or implementing the invention underthe claims. Some alternative implementations can include additionalelements to those implementations described above or include fewerelements.

Any patents and applications and other references noted above, and anythat may be listed in accompanying filing papers, are incorporatedherein by reference in their entireties, except for any subject matterdisclaimers or disavowals, and except to the extent that theincorporated material is inconsistent with the express disclosureherein, in which case the language in this disclosure controls. Aspectsof the invention can be modified to employ the systems, functions, andconcepts of the various references described above to provide yetfurther implementations of the invention.

To reduce the number of claims, certain implementations are presentedbelow in certain claim forms, but the applicant contemplates variousaspects of an invention in other forms. For example, aspects of a claimcan be recited in a means-plus-function form or in other forms, such asbeing embodied in a computer-readable medium. A claim intended to beinterpreted as a mean-plus-function claim will use the words “meansfor.” However, the use of the term “for” in any other context is notintended to invoke a similar interpretation. The applicant reserves theright to pursue such additional claim forms in either this applicationor in a continuing application.

What is claimed is:
 1. A method for wireless communication, comprising:initiating, by a first access node in a first type of communicationnetwork, an Internet Protocol Multimedia System (IMS) sessionestablishment for a wireless device; configuring, by the first accessnode, the IMS session establishment using a Protocol Data Unit (PDU)session modification request; and refraining from a fallback to a secondtype of communication network for the IMS session establishment.
 2. Themethod of claim 1, comprising: initiating a handover procedure by thefirst access node to handover the wireless device to a second accessnode of the second type of communication network after the IMS sessionestablishment is complete.
 3. The method of claim 1, wherein the IMSsession establishment comprises an IMS voice session establishment. 4.The method of claim 1, wherein the first type of communication networkcomprises a Fifth-Generation (5G) network and wherein the second type ofcommunication network comprises a Long-Term-Evolution (LTE) network. 5.The method of claim 1, wherein the refraining is based on a capabilityof the wireless device, the capability of the wireless device indicatingthat the wireless device supports Fifth-Generation (5G) communicationtechnology.
 6. The method of claim 1, wherein the refraining is based ona comparison of a first network condition of the first type ofcommunication network and a second network condition of the second typeof communication network.
 7. The method of claim 6, wherein the firstnetwork condition of the first type of communication network or thesecond network condition of the second type of communication networkcomprises at least one of a coverage area, a Reference Signal ReceivedPower (RSRP), or a Reference Signal Received Quality (RSRQ).
 8. A devicefor wireless communication connected to a first network, comprising oneor more processors that are configured to: initiate an Internet ProtocolMultimedia System (IMS) session establishment for a wireless device;configure the IMS session establishment using a Protocol Data Unit (PDU)session modification request; and refrain from a fallback to a secondnetwork for the IMS session establishment, wherein the second network isdifferent from the first network.
 9. The device of claim 8, wherein theone or more processors are configured to: initiate a handover procedureto handover the wireless device to the second network after the IMSsession establishment is complete.
 10. The device of claim 8, whereinthe IMS session establishment comprises an IMS voice sessionestablishment.
 11. The device of claim 8, wherein the first networkcomprises a Fifth-Generation (5G) network and wherein the second networkcomprises a Long-Term-Evolution (LTE) network.
 12. The device of claim8, wherein the one or more processors are configured to refrain from thefallback based on a capability of the wireless device, the capability ofthe wireless device indicating that the wireless device supportsFifth-Generation (5G) communication technology.
 13. The device of claim8, wherein the one or more processors are configured to refrain from thefallback based on a comparison of a first network condition of the firstnetwork and a second network condition of the second network.
 14. Thedevice of claim 13, wherein the first network condition of the firstnetwork or the second network condition of the second network comprisesat least one of a coverage area, a Reference Signal Received Power(RSRP), or a Reference Signal Received Quality (RSRQ) of the firstnetwork or the second network.
 15. A system of one or more wirelesscommunication networks, comprising: a first access node in a firstcommunication network; and a second access node in a secondcommunication network that is different from the first communicationnetwork, wherein the second access node is configured to: initiate, inthe second communication network, an Internet Protocol Multimedia System(IMS) session establishment for a wireless device; configure the IMSsession establishment using a Protocol Data Unit (PDU) sessionmodification request; and refrain from a fallback to the firstcommunication network for the IMS session establishment.
 16. The systemof claim 15, wherein the second access node is configured to: initiate ahandover procedure to handover the wireless device to the first networknode after the IMS session establishment is complete.
 17. The system ofclaim 15, wherein the IMS session establishment comprises an IMS voicesession establishment.
 18. The system of claim 15, wherein the firstcommunication network comprises a Long-Term-Evolution (LTE) network andthe second communication network comprises a Fifth-Generation (5G)network.
 19. The system of claim 15, wherein the second access node isconfigured to refrain from the fallback based on a capability of thewireless device, the capability of the wireless device indicating thatthe wireless device supports Fifth-Generation (5G) communicationtechnology.
 20. The system of claim 15, wherein the second access nodeis configured to refrain from the fallback based on a comparison of afirst network condition of the first communication network and a secondnetwork condition of the second communication network, wherein the firstnetwork condition of the first communication network or the secondnetwork condition of the second communication network comprises at leastone of a coverage area, a Reference Signal Received Power (RSRP), or aReference Signal Received Quality (RSRQ).